fix unsafe memory write in vtkImageGradientMagnitude etc

The class was writing to a memory location from
multiple threads bro. Also fix thread issues in
the TestAtomic and TestConditionVariable tests.

Common/Core/Testing/Cxx/TestAtomic.cxx

@@ -19,8 +19,6 @@
 
 #include <algorithm>
 
-static int Total = 0;
-static vtkTypeInt64 Total64 = 0;
 static vtkAtomicInt32 TotalAtomic(0);
 static vtkAtomicInt64 TotalAtomic64(0);
 static const int Target = 1000000;
@@ -29,17 +27,27 @@ static int Values64[Target+1];
 static vtkMTimeType MTimeValues[Target];
 static int NumThreads = 5;
 
+// uncomment the following line if you want to see
+// the difference between using atomics and not
+//#define SHOW_DIFFERENCE
+#ifdef SHOW_DIFFERENCE
+static int Total = 0;
+static vtkTypeInt64 Total64 = 0;
+#endif
 
 VTK_THREAD_RETURN_TYPE MyFunction(void *)
 {
   vtkNew<vtkObject> AnObject;
   for (int i=0; i<Target/NumThreads; i++)
   {
+#ifdef SHOW_DIFFERENCE
     Total++;
+    Total64++;
+#endif
+
     int idx = ++TotalAtomic;
     Values32[idx] = 1;
 
-    Total64++;
     idx = ++TotalAtomic64;
     Values64[idx] = 1;
 
@@ -96,9 +104,12 @@ VTK_THREAD_RETURN_TYPE MyFunction4(void *)
 
 int TestAtomic(int, char*[])
 {
+#ifdef SHOW_DIFFERENCE
   Total = 0;
-  TotalAtomic = 0;
   Total64 = 0;
+#endif
+
+  TotalAtomic = 0;
   TotalAtomic64 = 0;
 
   for (int i=0; i<=Target; i++)
@@ -160,8 +171,10 @@ int TestAtomic(int, char*[])
   mt->SetSingleMethod(MyFunction4, NULL);
   mt->SingleMethodExecute();
 
+#ifdef SHOW_DIFFERENCE
   cout << Total << " " << TotalAtomic.load() << endl;
   cout << Total64 << " " << TotalAtomic64.load() << endl;
+#endif
 
   if (TotalAtomic.load() != Target)
   {

Common/Core/Testing/Cxx/TestConditionVariable.cxx

+#include "vtkAtomicTypes.h"
 #include "vtkConditionVariable.h"
 #include "vtkMultiThreader.h"
 #include "vtksys/SystemTools.hxx"
@@ -8,7 +9,7 @@
 typedef struct {
   vtkMutexLock* Lock;
   vtkConditionVariable* Condition;
-  int Done;
+  vtkAtomicInt32 Done;
   int NumberOfWorkers;
 } vtkThreadUserData;
 

Imaging/General/vtkImageGradientMagnitude.cxx

@@ -143,7 +143,7 @@ void vtkImageGradientMagnitudeExecute(vtkImageGradientMagnitude *self,
   unsigned long target;
   int axesNum;
   int *wholeExtent;
-  vtkIdType *inIncs;
+  vtkIdType inIncs[3];
   double r[3], d, sum;
   int useZMin, useZMax, useYMin, useYMax, useXMin, useXMax;
   int *inExt = inData->GetExtent();
@@ -170,7 +170,7 @@ void vtkImageGradientMagnitudeExecute(vtkImageGradientMagnitude *self,
   r[2] = 0.5 / r[2];
 
   // get some other info we need
-  inIncs = inData->GetIncrements();
+  inData->GetIncrements(inIncs);
   wholeExtent = inData->GetExtent();
 
   // Move the starting pointer to the correct location.